: a trigonometric function that for an acute angle is the ratio between the leg adjacent to the angle when it is considered part of a right triangle and the hypotenuse
: a trigonometric function cos θ that for all real numbers θ is given by the sum of the alternating series and that is exactly equal to the cosine of an angle of measure θ in radians
Origin of COSINE
New Latin cosinus,
+ Medieval Latin sinus
First Known Use: 1635
Seen & Heard
What made you want to look up cosine? Please tell us where you read or heard it (including the quote, if possible).